To date, automobile door hinges made from sheet metal have been widely used, because they can be manufactured at low cost by press-forming or the like (see, for example, PTL 1).
The strength of existing automobile door hinges made from sheet metal is low. Therefore, door hinges used for large-sized cars or luxury cars, which have heavy doors, are made by cutting an extruded steel material to a predetermined length and by machining the cut steel material into a predetermined shape (see, for example, PTL 2).